To reheat frozen food so as to make it edible, there can be used a defrosting method such as defrosting frozen food by heating it over an open fire, defrosting frozen food by heating a vessel containing the frozen food in hot water, or defrosting frozen food by heating it in a microwave oven. Of these defrosting methods, microwave ovens make it possible to defrost frozen food easily and hygienically without making hands dirty, and are therefore generally widespread. Most of conventional microwave ovens have only so-called “warming” function or “microwave cooking” function of performing high-frequency heating of food, which is an object to be heated, by irradiating the food with microwaves. However, recently, with the diversification of food and the like, microwave ovens have become more and more multifunctional, and microwave ovens of a type having, in addition to the cooking functions using high-frequency heating, a so-called “steam cooking” function using steam heating are widely used (see Patent Literatures 1 and 2). While high-frequency heating has the advantage of short heating time, it has the disadvantages of being likely to result in uneven heating and also being likely to cause drying and hardening of the food if heated excessively. On the other hand, in steam heating, food is heated with steam generated by boiling water, and therefore, the disadvantages of high-frequency heating can be compensated for by combining high-frequency heating with steam heating.
Patent Literatures 3 to 5 disclose techniques for improving heating cookers having a microwave cooking function and a steam cooking function. In these techniques, a container accommodating food to be heated, is disposed in a heating chamber of a heating cooker, and the container is provided with an inlet port for steam supplied from a steam supplier, so that steam can be directly introduced into the container. A container (steam cooker) with a lid disclosed in Patent Literature 3 is configured such that an internal space of the container is partitioned into two, an upper and lower space, by a steam-permeable partition plate. In this container, food is accommodated in the upper space, and a steam inlet port is provided in a wall portion defining the lower space, so that steam can be directly introduced into the lower space. Containers disclosed in Patent Literatures 4 and 5 have a receiving tray on which food is to be placed and a grill tray lid that covers the receiving tray, the grill tray lid being provided with a steam inlet port. According to Patent Literatures 3 to 5, the techniques disclosed therein purport to enable food to be deliciously cooked while increasing cooking efficiency and reducing cooking time.
Patent Literature 6 discloses a technique that uses steam heating to defrost frozen food (pasta containing rice flour). The technique disclosed in Patent Literature 6 was made in view of the following problem: compared with ordinary pasta made from only wheat flour, pasta containing rice flour significantly deteriorates in quality when defrosted from a frozen state. The technique includes a step of keeping frozen pasta that contains rice flour and has been boiled and frozen under specific conditions, in steam at gauge pressure within a specific range for a specific period of time to thereby quickly defrost the frozen pasta. According to Patent Literature 6, the technique disclosed therein purports to make it possible to perform integrated management of the steps of boiling and freezing in a processing factory, the step of transporting from the processing factory to a store, and the steps of storing and quickly defrosting in the store, and to provide chewy pasta containing rice flour in a short period of time upon receiving an order.